The present invention relates to a continuous process for making building products by coating an expanded polymeric form with a facing material, preferably concrete, stucco or plaster.
Structural building blocks and non-structural mouldings made with a foam core and a concrete or plaster coating, are known. An example of such a structural building block with a concrete coating is shown in U.S. Pat. No. 4,774,794 to D. J. Grieb which issued Oct. 4, 1988. Generally, structural building blocks, made with a foam core and a concrete coating, allow interconnection with other blocks to produce a flat, two-sided panel for use in forming walls, floors, ceilings and related structures. It is preferable that the foam core be exposed on the edges where the panels interconnect so that there is a continuous core of insulating material. The building blocks tend to be impervious to humidity and water and resist cracking, rotting, weathering, fading and have other advantages
It is also known to make blocks, panels and mouldings with a foam core and a concrete exterior using either a batch process, or a continuous process. For example, a pultrusion process is known in which a preformed foam core slab is pulled through a pultrusion mandrel by a roller chain with caterpillar gripping pads. Concrete mixtures are then fed into the pultrusion mandrel on both sides of the foam core slab. After sufficient curing of the concrete, the foam core block so formed can be cut with a travelling carbide tipped cut-off saw. One of the difficulties of this process is that there are significant problems caused by fouling of the chain with concrete, because of leakage of concrete onto and between the gripping pads and onto the chain and related surfaces. In addition, setting up the pultrusion mandrel is extremely time consuming and additional processing is required to remove excess foam material. An improved process is highly desirable and the present invention is directed to providing such an improvement.
It is proposed to make such building blocks with an alternative continuous process. Surprisingly, it has been found that it is possible to make such building panels without the need to pull the foam core through the process.
The present invention provides a continuous process, with upstream and downstream longitudinal directions, for making an elongated coated building product comprising a longitudinal expanded synthetic polymeric form having a desired cross-sectional shape, and having a longitudinally continuous coating of a facing material on at least a portion of a periphery of the cross-sectional shape, said process comprising:
a) feeding the expanded synthetic polymeric form longitudinally into the inlet of an elongated guiding channel which comprises a longitudinally split mould having an internal cross-sectional shape suitable to produce a desired external cross-sectional shape of the coated building product;
b) guiding the expanded synthetic polymeric form along the guiding channel, without any means for pulling the expanded synthetic polymeric form after the expanded synthetic polymeric form enters the inlet of the guiding channel;
c) feeding the facing material into the split mould through a first aperture in a first mould section of the split mould.
In an embodiment, the facing material is selected from the group consisting of concrete, gypsum, plaster. The concrete, gypsum or plaster may contain strengthening materials, e.g. glass fibre, cellulosic fibre.
In one embodiment, the split mould is a two-part split mould and the facing material is additionally fed through a second aperture in a second mould section of the split mould, so that the facing material is coated on at least two opposing sides of the expanded synthetic polymeric form.
In another embodiment, facing material is prevented from escaping upstream towards the inlet by sealing means between the split mould and the expanded synthetic polymeric form.
In a further embodiment, the coated building product is a moulding strip with at least one exposed face of the expanded synthetic polymeric form, in which process the exposed face is in sliding contact with a second mould section of a two-part split mould which has no apertures therein for introduction of facing material.
In another embodiment, the building product is a moulding strip and the facing material is plaster.
In yet another embodiment the expanded synthetic polymeric form is made from expanded polystyrene, polyurethane, phenolic or polyisocyanurate.
In a further embodiment, the building product is a building panel which is coated on at least two sides with concrete, in which process the expanded form is guided between first and second mould sections of a two-part split mould, concrete facing material is fed through a first aperture in the first mould section and through a second aperture in the second mould section.
In yet another embodiment, the building product is a building panel which is coated on at least two sides with the facing material and ties are inserted transversely, at longitudinally spaced intervals, through the expanded form prior to feeding the expanded synthetic polymeric form longitudinally into the inlet of the elongated guiding channel, such that when the expanded form is coated with the facing material, opposing coatings of facing material are tied together by the ties.
In another embodiment, the expanded form and the facing material are mechanically locked by means of mating shapes of contracting faces of the facing material and the expanded form. Preferably the mating shape is in the form of a dovetail joint.
In another embodiment, the process for making the building panel comprises:
(a) feeding the expanded synthetic polymeric form longitudinally into the inlet of the guiding channel and first and second mould sections of a two-part split mould are slidingly sealed against at least one of upper and lower portions of the expanded form;
(b) feeding facing material, selected from the group consisting of concrete and gypsum, into the split mould through the first aperture in the first mould section and through the second aperture in the second mould section.
In one embodiment, the second aperture is downstream of said first aperture and there are sealing strips between the expanded synthetic polymeric form and the first and second mould sections, at positions slightly upstream of the first and second apertures.
In another embodiment, there is a back pressure plate between the second mould section and the expanded synthetic polymeric form between the inlet of the guiding channel and the sealing strip which is upstream of the second aperture.
In a further embodiment, the polymeric expanded material is continuously provided from an extrusion or fusion machine upstream of the inlet to the guiding channel.
The present invention also provides an apparatus for a continuous process, with longitudinal upstream and downstream directions, for making an elongated coated building product comprising a longitudinal expanded synthetic polymeric form, said apparatus comprising:
a) an elongated guiding channel which has a longitudinally split mould having an internal cross-sectional shape suitable to produce a desired external cross-sectional shape of the coated building product, said guiding channel having an inlet and an outlet;
b) means for guiding the expanded synthetic polymeric form along the guiding channel, without any means for pulling the expanded synthetic polymeric form after the expanded synthetic polymeric form enters the inlet of the guiding channel;
c) means for feeding facing material into the split mould through a first aperture in a first mould section of the split mould; and
d) sealing means in the guiding channel to prevent facing material escaping upstream between the expanded synthetic polymeric form and mould sections, towards the inlet of the guiding channel.
In one embodiment, there is means for feeding facing material into the split mould through a second aperture in a second mould section of the split mould.
In another embodiment, the second aperture is downstream of said first aperture and there is a sealing strip between the polymeric expanded material and the second mould section at a position slightly upstream of the second aperture.
In a further embodiment, an extrusion or fusion machine for continuously making polymeric expanded material is provided upstream of the inlet to the guiding channel, for feeding polymeric expanded material into the inlet of the guiding channel.
In yet another embodiment, there is means for inserting ties transversely through the expanded form, at longitudinally spaced intervals, between the extrusion or fusion machine and the inlet to the guiding channel, such that ends of the ties will protrude into the facing material.